The metabolic reconstruction looks to be much too complex to understand in its entirety. They didn't test DNA as a nutrient, but did test nucleotides and nucleosides and deoxyribose (all supported growth as carbon sources both in silico and in vivo, and the nucleotides and nucleosides also served as nitrogen sources. I'm going to email the author asking for his perspective on whether B. subtilis should be able to use DNA as a carbon and nitrogen source.